Blood Pressure

Question 1

How is blood pressure regulated in the short term?

Answer 1

Baroreceptor reflex
(Adjust sympathetic and parasympathetic input to the heart to alter CO, adjust sympathetic input to peripheral resistance vessels to alter TPR)

Question 2

How is the blood pressure maintained over medium and longer time periods?

Answer 2

Complex interactions of neurohumeral responses

Directed at controlling sodium balance and thus extracellular fluid volume

Question 3

How can controlling Na+ levels control plasma volume and ultimately blood pressure?

Answer 3

By changing the sodium levels you can change the extracellular fluid volume.
Plasma is part of the extracellular fluid compartment so technically controlling na+ you can control the plasma volume and plasma volume affects heart rate

Question 4

What are the four pathways in which there is neurohumoral control over the circulation volume and hence BP?

Answer 4

1. Renin-angiotensin-aldosterone system
2. Sympathetic nervous system
3. Antidiurectic hormone (ADH)
4. Atrial natriuretic peptide (ANP)

Question 5

What factors stimulate the release of renin from the kidneys?

Answer 5

A) reduced NaCl delivery to distal tube (the macula densa cells to be precise)

B) reduced perfusion pressure (fall in BP) in the kidney causes the release of renin (detected by baroreceptors in afferent arteriole)

C) sympathetic stimulation to juxtaglomerular apparatus increases release of renin

Question 6

Where is renin released from?

Answer 6

Granular cells of juxtaglomerular apparatus in the kidneys (JGA)

These granular cells surround the afferent arteriole entering the glomerulus. They are located close to the distal tube which is surrounded by macula dense cells.

Question 7

What are the two types of angiotensin II receptors?

Answer 7

AT1 - main actions via this one (gpcr)

AT2

Question 8

What effect does angiotensin II have at the following sites:

1. Arterioles
2. Kidney
3. Sympathetic NS
4. Adrenal cortex
5. Hypothalamus

Answer 8

1. Vasoconstriction
2. Stimulates Na+ reabsorption at the kidneys
3. Increased release of Noradrenaline
4. Stimulates release of aldosterone
5. Increases thirst sensation (+ stimulates ADH release)

Question 9

Where is aldosterone released from?

Answer 9

The adrenal cortex

Question 10

What are the actions of aldosterone?

Answer 10

• stimulates Na+ and there water reabsorption
• activates apical Na+ channels (ENaC= epithelial Na channel) and apical K+ channel
• increases basolateral Na+ extrusion via Na/K/ATPase

Question 11

What effect does aldosterone have on potassium?

Answer 11

It lower levels of K+

Question 12

Where is ACE found?

Answer 12

Lungs predominantly (in epithelial cells)

Question 13

What does ACE do? (2)

Answer 13

1. It converts angiotensin I to angiotensin II

2. Converts bradykinin to peptide fragments

Question 14

How does ACE’s action on bradykinin help to raise blood pressure?

Answer 14

Because bradykinin has vasodilator actions and breaking it down means there is less vasodilation

Question 15

What is a side effect of ACE inhibitors and why does this happen?

Answer 15

Bad/dry cough

If ACE is inhibited then it doesn’t break down bradykinin

The accumulation of bradykinin causes the cough

Question 16

Give an example of an ACE inhibitor

Answer 16

Captopril, lisinopril, perindopril, enalapril

Question 17

In what way does the sympathetic NS raise blood pressure? (2)

Answer 17

Causes vasoconstriction of arterioles=increases BP (short term)

This vasoconstriction decrease the renal blood flow which stimulates Na+ retention which has a long term effect of raising your blood pressure

Question 18

How is Na+ retained by stimulation of the sympathetic NS?

Answer 18

Activation of the apical Na/H-exchanger and basolateral Na/K/ATPase in PCT

The lack of blood flow also stimulates the renin release from juxtaglomerular cells leading to increased Ang II levels and aldosterone levels which further increased Na+ reabsorption

Question 19

What is the main function of the ADH?

Answer 19

Formation of concentrated urine by retaining water to control plasma osmolarity

It increases water reabsorption in the distal nephrons

Question 20

What is ADH stimulated by?

Answer 20

Plasma osmolarity or severe hypovolaemia

Question 21

What system is in place to lower BP over the long term?

Answer 21

ANP (atrial Natriuretic peptides)

Question 22

How do ANPs work?

Answer 22

Cause vasodilation of afferent arteriole

Increase blood flow to glomerulus

Inhibits Na+ reabsorption

Water retained

BP raised

Question 23

What are prostaglandins?

Answer 23

Act as vasodilator locally

(PGE2) Enhance glomerular fitatrion and reduce Na+ reabsorption

Can have important protective function: Act as buffer to excessive vasoconstriction produced by SNS and RAA system

Important when levels of Ang II are high

Question 24

What role does dopamine play in manning blood pressure?

Answer 24

Formed locally in the kidneys from circulating L-DOPA

Causes vasodilation and increases renal blood flow

Reduce reabsorption of NaCl (inhibits NaH exchanger and Na/K ATPase in principle cells of PCT and TAL)

Question 25

What clinical use does dopamine have?

Answer 25

Used to treat Parkinson’s disease

Will lower BP so need to be aware of that!

Dopamine is not used as an antihypertensive